Shadeless mesh that's being affected by lighting?
What you describe is not a shadeless material.
You can try and mix an Emission shader with another non emitting shaders like Diffuse or Glossy shader, giving you a blend between shadelessness and light interaction with your scene.
Just connect a Shader Mix node input sockets to different combinations of emission/diffuse/glossy and try them yourself.
Alternatively look into an Ambient Occlusion shader node. It doesn't react to scene light, instead being self shadowed by other geometry only. If correctly setup with a low distance value it can simulate shadelessness to a certain extent while keeping proximity shadows.
One final note, if you are not looking for photo realism and instead rendering lost of NPR stylized stuff Cycles, being a physically based render engine, may not be the most indicated for you. There are other faster less resource hungry engines out there that may be better suited for your work, like Blender Internal or even simply the OpenGL viewport.